The present invention relates to a liquid sampling bench and particularly to a bench for taking radioactive liquid samples.
The remote taking of active solution samples in chemical units for the processing of irradiated fuels is carried out by means of so-called "sampling benches".
The vessels containing the radioactive liquids to be sampled are located beneath a biological protection slab, whose upper part serves as a working plane. The vessels are located at distances, which can represent several dozen meters. The liquid to be sampled is raised from these vessels to the level of the sampling bench and preferably continuously circulates. The plug, which is made from a flexible and elastic material, of a container called a jug or pot, which is previously placed under vacuum, is pricked at its end by a needle connected to the stream of liquid to be sampled. After filling, the container is transferred from the sampling bench to an analytical laboratory. Such benches are described in French Pat. Nos. 1 401 298, and 1 401 405, as well as in certificate of addition No. 2 058 751 to French Pat. No. 1 401 298. These known benches essentially comprise, within a glove box, a series of liquid intakes by means of hollow needle end fittings connected to the vessels containing the radioactive liquids to be dosed, means for introducing the containers into the glove box and for removing the containers from the glove box, whereby handling means make it possible to displace the containers within the glove box. The handling means are fixed to a tool holder and are in general of three types, namely an unplugging tool for the needle intake end fittings, a container handling tool and a tool for removing and refitting the needles.
In such benches, the ends of the end fittings are arranged in accordance with at least one circumferential arc. Above these end fittings and within the glove box, there is a support which rotates about a first axis. On said support a tool holder can rotate about a second axis differing from the first, whilst said tool holder can also move along the second axis. The tools to be used for taking the samples are positioned on the tool holder, in positions off-centred parallel to the second axis and equidistant therefrom.
French certificate of addition No. 2 058 751 describes a number of improvements whereof one relates to an easily changeable short needle end fitting.
These sampling benches operate correctly, but have a certain number of disadvantages. Firstly the benches of the above type are disposed within a glove box, which is itself positioned above the concrete biological protection slab. To provide protection against alpha particles, the system of panels of the glove box and the tools are mounted with gaskets. Furthermore, in order to provide protection against gamma rays, it is necessary for the upper mechanical part of the tools to be formed from solid members corresponding to a protection of at least 7 cm of lead. Moreover, the periphery of the bench is surrounded by lead plates and the face on the working side is provided with a porthole and tongs for performing manipulations in the glove box. In this case, the glove box and its biological protection means form a cumbersome and very heavy assembly.
Certificate of addition No. 2 058 751 proposes the automatic extraction of the filled container and the transportation thereof out of the vessel bench by means of a pneumatic outlet means. For this purpose a mechanical device for the conditioning and removal of the container is described, which makes it possible to automatically confine the container in a slide and to pneumatically remove the container-slide assembly. These mechanical devices are relatively complex and it is desirable to limit their number in order to increase the reliability of the apparatus system.
Moreover, in the aforementioned benches, the end fittings have a certain slope, instead of being positioned vertically. The tools also have a certain slope with respect to the vertical and operate in accordance with an oblique axis. This arrangement made necessary by the very design of the benches with several end fittings described in the aforementioned patent necessitates a precise positioning and an accurate mechanical construction, whose reliability may be inadequate. Finally, when the container, after filling, is removed from the needle end fitting, a drop is left behind on the outer surface of the flexible, elastic plug, perforated by the needle and said drop can be a dangerous source of contamination.